CI build for iOS app

[tillahoffmann]

@biblicabeebli, following on from our discussion yesterday, I'm going to set up a bit of testing infrastructure around the iOS app so I don't break anything in the process of exploring our new feature.

The main changes are

• use rbenv to isolate ruby environment for reproducible builds
• work around the bug in the unmaintained library using a post-install hook
• add GitHub Action to build the app

[biblicabeebli]

Do you have an idea of what the git ~server cost is to do a build of this.

Straight up, I am ignorant about this, I have no idea what our resource usages are here - I just know that building the iOS app is going to be a solid order of magnitude more than any other task we have.

(We do have automated builds of Android, but JVM builds are way less than a swift compile)

@hydawo - you might be able to answer this stuff.

[tillahoffmann]

GitHub Action is free for public repositories, I think (https://docs.github.com/en/billing/concepts/product-billing/github-actions#how-use-of-github-actions-is-measured).

[biblicabeebli]

That's good to know that there is free stuff, but skimming that indicates freenness is a monthly quota system based on account type....

Oh there it is, public repos, you're right.

Awesome. I assume there are a bunch of build credentials and details of things I would need to provide too.

(Not going to make this one a priority rn)

[tillahoffmann]

I think there's two pieces here: build and deploy. Deploy would require credentials etc, but build works as is.